In general, the distal end portion of an endoscope is provided with components, such as an illumination optical system for radiating illumination light to an object, an observation optical system for observation of the object, a channel for guiding a treatment instrument and etc., a nozzle for cleaning the lens surface of the observation optical system, and the like. Further, an endoscope which is capable of efficiently illuminating a field of view having a wide angle of view by providing a plurality of the illumination optical systems has also been proposed. As such endoscopes, for example, PTL 1 discloses an endoscope which has an observation window of an observation optical system, a forceps opening whose diameter is larger than that of the observation window, and a plurality of illumination windows for radiating illumination, which are located in the distal end surface of the inserted portion. The plurality of illumination windows are located so that the observation window is located between the illumination windows, the illumination angle and light distribution of the illumination optical system disposed at position adjacent to the observation optical system is wide.